SimpleITK  1.3.0.dev466
sitkEnableIf.h
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1 /*=========================================================================
2 *
3 * Copyright Insight Software Consortium
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0.txt
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 *=========================================================================*/
18 #ifndef sitkEnableIf_h
19 #define sitkEnableIf_h
20 
21 namespace itk
22 {
23 namespace simple
24 {
25 
26 /* \brief This is an implementation of the enable if idiom.
27  *
28  * This template enables specialization of a templated function based
29  * on some traits or concepts. It is implemented with SFINAE.
30  *
31  * If the parameter V is true then the Type trait is the second
32  * template parameter, otherwise an implementation does not exist and
33  * with SFIANE another implementation may be chosen.
34  *
35  * Example:
36  * \code
37  * template<class TImageType>
38  * typename EnableIf<IsBasic<TImageType>::Value>::Type
39  * AllocateInternal ( unsigned int Width, unsigned int Height, unsigned int Depth );
40  *
41  * template<class TImageType>
42  * typename EnableIf<IsVector<TImageType>::Value>::Type
43  * AllocateInternal ( unsigned int Width, unsigned int Height, unsigned int Depth );
44  * \endcode
45  *
46  */
47 template <bool V, class T = void> struct EnableIf {};
49 template <class T> struct EnableIf<true, T> { typedef T Type; };
53 /* \brief An implementation of the negation of the enable if idiom.
54  *
55  * \sa EnableIf
56  */
57 template <bool V, class T = void> struct DisableIf {};
59 template <class T> struct DisableIf<false, T> { typedef T Type; };
62 }
63 }
64 
65 #endif // sitkEnableIf_h